The present invention relates to cable interconnection between electronic equipment and, more particularly, to a connector and/or cable capable of selectively opening or closing a ground connection between two pieces of electronic equipment.
Noise problems often occur when undesirable ground loops are produced. Such ground loops are often formed when multiple pieces of electronic equipment are connected to one another through cables. To illustrate this problem, reference is made to FIG. 1, which shows a first piece of electronic equipment 10 connected to a second piece of electronic equipment 20 by way of a cable 30. The cable 30 includes a first connector 32 and a second connector 34 that are operable to mate with the first piece of electronic equipment 10 and the second piece of electronic equipment 20, respectively. The cable 30 also includes signal wires 36a, 36b and a ground wire 36c for electrically connecting respective signal and ground leads 12, 14, 16 of the first piece of electronic equipment 10 to signal and ground leads 22, 24, 26 of the second piece of electronic equipment 20. The first piece of electronic equipment 10 includes a connection from earth ground 1 to ground lead 16 (and/or chassis). Similarly, the second piece of electronic equipment 20 includes a connection from earth ground 2 to ground lead 26 (and/or chassis).
An undesirable ground loop may be produced when the cable 30 electrically connects the ground lead 16 of the first piece of electronic equipment 10 to the ground lead 26 of the second piece of electronic equipment 20. This is so because the respective earth grounds 1, 2 of the first and second pieces of electronic equipment 10, 20, respectively, are not at precisely the same potential as a function of time. Thus, noise currents flow between the earth grounds 1, 2 by way of the ground wire 36c of the cable 30. The connections to the respective earth grounds 1, 2 are often made by way of respective AC power cords and chassis connections for the first and second pieces of electronic equipment 10, 20. Consequently, the noise currents are often in the audible range, for example, 60 Hz, 120 Hz, 180 Hz, etc. (often referred to as xe2x80x9chumxe2x80x9d).
With reference to FIG. 2, the ground loop problem illustrated in FIG. 1 may be solved by replacing the first piece of electronic equipment 10 with a piece of electronic equipment 40 that includes a switch 42 that is operable to interrupt the electrical path between the earth ground 1 and the ground lead 16. Unfortunately, very few pieces of electronic equipment include such a switch 42. When a piece of electronic equipment includes such a switch 42, it often is a very high-end unit with a correspondingly high purchase price. Consequently, users often opt for the electronic equipment 10, 20 of FIG. 1 and either live with the undesirable hum or take other, less advantageous, approaches to eliminating the noise currents. For example, users may attempt to disconnect the earth ground 1 from, for example, the first piece of electronic equipment 10 by removing the earth ground terminal from the AC power cord or utilizing a three-prong to two-prong adapter (often called a xe2x80x9ccheaterxe2x80x9d), which performs the same function. In either case, the chassis of the first piece of electronic equipment 10 will float with respect to earth ground 1 and, therefore, present an electrical shock hazard to those handling the first piece of electronic equipment 10.
With reference to FIG. 3, it is noted that a cable 50 may include a connector 52 having a switch 58 coupled between signal leads 54, 56. In order to achieve a mute condition, a user may connect leads 54, 56 together by way of the switch 58 (thereby shorting any differential signal from reaching the second piece of electronic equipment 20). The muting switch 58, however, does not solve the ground loop problem between earth grounds 1, 2.
Accordingly, there is a need in the art for a connector and/or cable that can effectively eliminate ground loop noise problems while still maintaining one or more signal connections between equipment.
In accordance with at least one aspect of the present invention, a signal cable includes: a first connector having at least one signal lead and a ground lead, and being operable to couple to a first mating connector of a first piece of electronic equipment; a second connector having at least one signal lead and a ground lead, and being operable to couple to a second mating connector of a second piece of electronic equipment; at least one signal wire and a ground wire electrically connecting the respective at least one signal leads and the respective ground leads of the first and second connectors; and at least one switch disposed with at least one of the first and second connectors, the at least one switch having selectable make/break contacts coupled between the ground lead and the ground wire of the at least one of the first and second connectors such that an electrical path between the ground leads of the first and second connectors may be selectively opened and closed.
Preferably, the first and second mating connectors of the first and second pieces of electronic equipment each include at least one mating signal lead and a mating ground lead for connection to the respective at least one signal lead and ground lead of one of the first and second connectors; the mating ground leads are electrically connected to respective chassis grounds of the first and second pieces of electronic equipment; and the at least one switch is operable to selectively open and close an electrical path between the chassis grounds of the first and second pieces of electronic equipment.
In accordance with at least one further aspect of the present invention, a connector operable to couple to a mating connector of a piece of electronic equipment includes: at least one signal lead and a ground lead operable to electrically connect to at least one signal wire and a ground wire, respectively, of a cable; and at least one switch having selectable make/break contacts, one of the make/break contacts being electrically connected to the ground lead and the other make/break contact being operable to electrically connect to the ground wire of the cable such that an electrical path between the ground lead and the ground wire may be selectively opened and closed.
In accordance with at least one further aspect of the present invention, a system includes: a first piece of electronic equipment having a first mating connector that includes at least one mating signal lead and a mating ground lead, the ground lead being electrically connected to a chassis ground of the first piece of electronic equipment; a second piece of electronic equipment having a second mating connector that includes at least one mating signal lead and a mating ground lead, the ground lead being electrically connected to a chassis ground of the second piece of electronic equipment; and a signal cable including: a first connector having at least one signal lead and a ground lead, and being operable to couple to the first mating connector of the first piece of electronic equipment; a second connector having at least one signal lead and a ground lead, and being operable to couple to the second mating connector of the second piece of electronic equipment; at least one signal wire and a ground wire electrically connecting the respective at least one signal leads and the respective ground leads of the first and second connectors; and at least one switch disposed with at least one of the first and second connectors, the at least one switch having selectable make/break contacts coupled between the ground lead and the ground wire of the at least one of the first and second connectors such that an electrical path between the chassis grounds of the first and second pieces of electronic equipment may be selectively opened and closed.
In accordance with at least one further aspect of the invention, a connector operable to couple between a mating connector of a piece of electronic equipment and a mating connector of a cable, includes: a first end having at least one signal lead and a ground lead operable to electrically connect to at least one mating signal lead and a mating ground lead, respectively, of the mating connector of the piece of electronic equipment; a second end having at least one signal lead and a ground lead operable to electrically connect to at least one signal wire and a ground wire, respectively, of the mating connector of the cable; and at least one switch having selectable make/break contacts, one of the make/break contacts being electrically connected to the ground lead of the first end and the other make/break contact being operable to electrically connect to the ground lead of the second end such that an electrical path between the ground leads may be selectively opened and closed.